Green lasers are advantageous over more widely used red lasers for a variety of reasons. Green lasers are easier on the human eye, more perceptible to a user, and more capable of providing clearer, projected images for users.
Most green lasers, a prior art example of which is shown in FIG. 1, suffer from a variety of drawbacks. First, power efficiency is relatively low, typically about 7% or less. Second, such lasers are only operable among very limited temperature ranges. Additionally, modulation speed is very limited. Other potential drawbacks of present green laser technologies include heat, cost and package size.
FIG. 2 shows a typical structure for a prior art green laser diode. A lens 202 is positioned in front of a laser diode 201 with so that the laser diode 201 excites a crystal to emit light at 1064 nanometers. The 1064 nanometer light is used to excite a nonlinear crystal such as KTP crystal, to generate second harmonic wave at 532 nanometers. This green laser light is then processed through beam expansion optics 205 as shown in FIG. 2. This prior arrangement suffers from several of the above described problems, including increased heat generation and package size.
An additional prior art green laser arrangement is shown in FIG. 3. A 1064 nanometer laser diode is arranged so that its output is processed through lenses 302 and focused on a PPMgLN crystal waveguides on a temperature controlled plate. The output from the nonlinear optical waveguide is processed through a collimating lens and color-filter 305, resulting in a green laser output beam via single pass second harmonic generation.
The arrangement shown in FIG. 3 is also subject to certain drawbacks. For example, there is a narrow temperature range over which such a device can operate, after which performance and power drastically degrade. Moreover, there are a large number of parts as shown in FIG. 3, some of which can be expensive. Further, in order to obtain sufficient power conversion efficiency, it is critical that all of the components be aligned properly, resulting in a complex and expensive manufacturing process, that utilizes many expensive parts.
There exists a need in the art for a more efficient and cost effective technology for producing green lasers.